The present invention relates to barrier systems for protecting surfaces, and more particularly to a water-based primer useful for facilitating bonding of a barrier membrane to substrates such as concrete, gypsum, wood, and fiber board.
As organic solvents in the work place have come under increased regulatory scrutiny, it is desired to use water-based compositions when possible. U.S. Pat. No. 4,897,313 of Wiercinski disclosed a waterproofing system for sealing concrete building surfaces, wherein a water-based latex primer composition, comprising butylacrylate, styrene, and acrylonitrile, was disposed upon a concrete surface to facilitate the subsequent attachment thereto of a waterproofing membrane having a pressure-sensitive adhesive on a plastic carrier sheet. An acrylate latex suitable for formulating the primer, available from Union Carbide under the name UCAR Latex 123, could be diluted from its original viscosity of 150 centipoise (cp) to a usable range of 1-100 cp (Brookfeld viscosity at 50 rpm, 25xc2x0 C.), and more preferably to 5-20 cp, the preferred range for achieving optimum penetration into porous concrete surfaces.
As another example, U.S. Pat. No. 5,270,373 of Wiercinski et al. disclosed a variety of aqueous-based emulsion polymer primers for enhancing the bond of waterproofing membranes to building structure surfaces such as subsurface basements, foundations, concrete walls, retaining walls, and others. Of particular concern was that adhesion of the preformed waterproofing membranes to the concrete surfaces was diminished by the presence of dust particles which covered the cement or concrete walls. Priming (or pretreatment) was required especially in these instances because the ability of the waterproofing membrane to form a bond with the cement or concrete surface was decreased by the particles. Examples of polymers used in the primers included styrene butadiene rubber, styrene butadiene styrene, natural rubber, polybutadiene, polyvinyl acetate, acrylic polymer, chloroprene, polyurethane, copolymers of ethylene and vinyl acetate, or copolymers of vinyl chloride and acrylics (Col. 2, lines 58-65). As a preferred example of a primer composition, Wiercinski et al. taught an SBR emulsion stabilized with potassium oleate.
It is also desired to apply membranes as weather barriers onto gypsum wall boards using water-based primer compositions. However, gypsum wall boards of recent design have glass fibers embedded within a water-resistant gypsum core. Such boards are seen frequently used on new school and office buildings as external support for a xe2x80x9chouse wrap,xe2x80x9dsuch as DuPont""s TYVEK(copyright) nonwoven fabric, covered subsequently by clapboard sheathing. It has been difficult to substitute the fabric housewrap with a pressure-sensitive adhesive barrier membrane, because it has hitherto been necessary to use solvent-based primers to facilitate bonding of the barrier membrane adhesive to the fiber-embedded gypsum board, and the water-based primers developed for concrete waterproofing use have not been found to facilitate barrier membrane bonding to gypsum boards.
Accordingly, a novel water-based primer system is needed that would permit additional pretreatment applications such as gypsum boards, fiber-embedded gypsum boards, and fiber-containing boards, in addition to cement and concrete structural surfaces.
In surmounting the disadvantages of the prior art, the present invention provides a barrier membrane package system having a water-based primer operative to enhance bonding of the membrane to difficult surfaces such as gypsum boards, fiber-embedded gypsum boards, fiber boards, as well as to cement, concrete, masonry block, and other surfaces.
An exemplary package system of the invention therefore comprises: (a) a membrane comprising a carrier sheet and a pressure-sensitive adhesive thereon; and (b) a primer composition comprising an aqueous dispersion operative to promote adhesion of said membrane to a construction surface, said primer composition having a viscosity of 200-2000 cp and more preferably 400-600 cp (Brookfield/#5 spindle/50 rpm, 25xc2x0 C.) and comprising a copolymer having at least two polymers selected from acetate, maleate, and acrylate. The copolymer is preferably an acetate-dioctyl maleate-2-ethylhexyl acrylate. An exemplary method for protecting a construction surface, comprising applying the primer composition to promote adhesion between the surface and the subsequently applied barrier membrane, is also described herein and after.
The term xe2x80x9cpackagexe2x80x9d as used herein means and refers both to the situation wherein the barrier membrane and primer are provided together as a system, and also to the situation in which the primer composition and barrier membrane are applied to a construction surface (e.g., a glass-embedded gypsum board) for xe2x80x9cpackagingxe2x80x9d the board itself or as an integrated part of a building structure.
Other advantages and features of the invention may become more apparent in the detailed description that follows.